Karl Johan Schuster (Swedish: [ˈjuːˈan ˈɧʏstɛr]; born 1 February 1985), known professionally as Shellback, is a Swedish songwriter, record producer, and musician. Shellback was listed as the No. 1 producer of 2012 on Billboard magazine's year end chart, and he also topped the list of their "Top 10 Songwriters Airplay Chart" the same year; he has won two Grammy Awards.
Work with Katy Perry
He worked with Katy Perry on the following songs:
Songs from Witness (2017):